This invention relates to current responsive, gas-actuated electrical connectors of the type embodied in a bushing plug for use in power distribution systems.
Electrical connectors of the type utilizing arc-responsive material for evolving arc-quenching gas in response to an arc being struck between movable electrodes and wherein the gas pressure is utilized to extinguish the arc are known and have been widely used in the art. These connectors are generally divided into three types the first of which is exemplified by U.S. Pat. No. 3,474,386 which utilizes a moving female contact constrained for movement within a piston assembly and wherein current is transferred to the fixed electrode of the bushing plug by means of a flexible copper cable. The piston or moving female contact assembly moves during normal switching operations, and during a fault closure the female contact is propelled by gas pressure to move into engaging connection with the advancing male electrode of the elbow connector. The second type of current responsive, gas-actuated electrical connector is exemplified in U.S. Pat. No. 3,958,855. This type of connector utilizes an auxiliary contact which moves in response to gas pressure developed during a fault closure operation and functions to transfer the arc struck between the male electrode and the stationary female contact to a remote point of the bushing plug which is removed from the arc-responsive material of the bushing plug. The third type of bushing plug is exemplified in U.S. Pat. No. 4,088,383, which is assigned to the same assignee as the present invention, wherein the female contact is carried by a moving assembly which transfers current to the fixed electrode of the bushing plug by means of a sliding contact.
These prior art bushing plugs suffer from one or more disadvantages such as the cost of making a reliable sliding or flexible connection for the current levels which must be handled during normal switching operations and/or fault-closure operations. The metal piston assemblies of these devices are also expensive and the large diameters of the piston assemblies require an undesired dimensional reduction of the surrounding bushing insulation and therefore a corresponding reduction in electrical performance. Further, the auxiliary contact or arcing ring device does not establish positive contact with the male electrode of the elbow connector which, therefore, decreases its fault-closure performance and specifications.
These and other disadvantages are overcome by the present invention wherein there is provided a bushing plug including a moving assembly which is lighter and therefore has a lower inertia providing faster response which also reduces arcing time. In a normal operation, and in its fully closed position, the bushing plug of the present invention provides a direct path for current which is not required to pass through sliding contacts or flexible cables. Further, improved electrical stress relief is accomplished as a result of the relatively small diameter of the metallic insert body which is provided coaxially with the surrounding elastomeric housing.